As for a SkyFrame, a TimeFrame is a Frame () and also a
Mapping (
), so it inherits all the properties and
behaviour of these two ancestral classes. When used as a Mapping, a
TimeFrame implements a unit transformation, exactly like a basic Frame
(
) or a UnitMap, so this aspect of its
behaviour is not of great importance.
When used as a Frame, however, a TimeFrame represents a wide range of
different 1-dimensional coordinate system which can be used to describe
moments in time. Absolute times and relative (i.e. elapsed) times are
supported (attribute TimeOrigin), as are a range of different time scales
(attribute TimeScale). An absolute or relative value in any time scale can
be represented in different forms such as Modified Julian Date, Julian Epoch,
etc (attribute System). AST extends the definition of these systems to
allow them to be used with any unit of time (attribute Unit). The TimeFrame
class also allows times to formatted as either a simple floating point value
or as a Gregorian date and time of day (attribute Format).
AST A Library for Handling World Coordinate Systems in Astronomy